The recent introduction of acetylene-terminated polyimides to produce cured reaction products which are stable at very high temperatures of 450.degree. C. and up has created an interest and need to produce the polyimides at attractive and competitive costs. The prime difficulty in the preparation of the acetylene-terminated polyimides which are described, for example, in U.S. Pat. No. 3,845,018 and U.S. Pat. No. 3,879,349, both to Norman Bilow et al, is the preparation of the monomers which include in one instance the preparation of meta-aminophenylacetylene (APA). This invention relates to the discovery of an unsupported cobalt polysulfide catalyst which selectively converts certain nitroaromatic acetylene compounds used in the process of this invention, e.g. nitrophenylacetylene, to the desired APA or substituted APA.